NDB wl-1533 tux optim 17 - allow slack in interior nodes

ndb/include/kernel/ndb_limits.h

@@ -110,7 +110,7 @@
  */
 #define MAX_TTREE_NODE_SIZE 64		// total words in node
 #define MAX_TTREE_PREF_SIZE 4		// words in min prefix
-#define MAX_TTREE_NODE_SLACK 3		// diff between max and min occupancy
+#define MAX_TTREE_NODE_SLACK 2		// diff between max and min occupancy
 
 /*
  * Blobs.

ndb/src/kernel/blocks/dbtux/Dbtux.hpp

@@ -591,7 +591,7 @@ private:
   void nodePopDown(Signal* signal, NodeHandle& node, unsigned pos, TreeEnt& ent);
   void nodePushDown(Signal* signal, NodeHandle& node, unsigned pos, TreeEnt& ent);
   void nodePopUp(Signal* signal, NodeHandle& node, unsigned pos, TreeEnt& ent);
-  void nodeSlide(Signal* signal, NodeHandle& dstNode, NodeHandle& srcNode, unsigned i);
+  void nodeSlide(Signal* signal, NodeHandle& dstNode, NodeHandle& srcNode, unsigned cnt, unsigned i);
   // scans linked to node
   void linkScan(NodeHandle& node, ScanOpPtr scanPtr);
   void unlinkScan(NodeHandle& node, ScanOpPtr scanPtr);
@@ -600,8 +600,19 @@ private:
   /*
    * DbtuxTree.cpp
    */
+  // add entry
   void treeAdd(Signal* signal, Frag& frag, TreePos treePos, TreeEnt ent);
+  void treeAddFull(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos, TreeEnt ent);
+  void treeAddNode(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos, TreeEnt ent, NodeHandle parentNode, unsigned i);
+  void treeAddRebalance(Signal* signal, Frag& frag, NodeHandle node, unsigned i);
+  // remove entry
   void treeRemove(Signal* signal, Frag& frag, TreePos treePos);
+  void treeRemoveInner(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos);
+  void treeRemoveSemi(Signal* signal, Frag& frag, NodeHandle node, unsigned i);
+  void treeRemoveLeaf(Signal* signal, Frag& frag, NodeHandle node);
+  void treeRemoveNode(Signal* signal, Frag& frag, NodeHandle node);
+  void treeRemoveRebalance(Signal* signal, Frag& frag, NodeHandle node, unsigned i);
+  // rotate
   void treeRotateSingle(Signal* signal, Frag& frag, NodeHandle& node, unsigned i);
   void treeRotateDouble(Signal* signal, Frag& frag, NodeHandle& node, unsigned i);
 

ndb/src/kernel/blocks/dbtux/DbtuxDebug.cpp

@@ -178,16 +178,19 @@ Dbtux::printNode(Signal* signal, Frag& frag, NdbOut& out, TupLoc loc, PrintPar&
     out << "occupancy " << node.getOccup() << " of interior node";
     out << " less than min " << tree.m_minOccup << endl;
   }
-  // check missed half-leaf/leaf merge
+#ifdef dbtux_totally_groks_t_trees
+  // check missed semi-leaf/leaf merge
   for (unsigned i = 0; i <= 1; i++) {
     if (node.getLink(i) != NullTupLoc &&
         node.getLink(1 - i) == NullTupLoc &&
-        node.getOccup() + cpar[i].m_occup <= tree.m_maxOccup) {
+        // our semi-leaf seems to satify interior minOccup condition
+        node.getOccup() < tree.m_minOccup) {
       par.m_ok = false;
       out << par.m_path << sep;
       out << "missed merge with child " << i << endl;
     }
   }
+#endif
   // check inline prefix
   { ConstData data1 = node.getPref();
     Uint32 data2[MaxPrefSize];

ndb/src/kernel/blocks/dbtux/DbtuxMeta.cpp

@@ -211,11 +211,7 @@ Dbtux::execTUX_ADD_ATTRREQ(Signal* signal)
       // make these configurable later
       tree.m_nodeSize = MAX_TTREE_NODE_SIZE;
       tree.m_prefSize = MAX_TTREE_PREF_SIZE;
-#ifdef dbtux_min_occup_less_max_occup
       const unsigned maxSlack = MAX_TTREE_NODE_SLACK;
-#else
-      const unsigned maxSlack = 0;
-#endif
       // size up to and including first 2 entries
       const unsigned pref = tree.getSize(AccPref);
       if (! (pref <= tree.m_nodeSize)) {

ndb/src/kernel/blocks/dbtux/DbtuxNode.cpp

@@ -386,19 +386,20 @@ Dbtux::nodePopUp(Signal* signal, NodeHandle& node, unsigned pos, TreeEnt& ent)
 }
 
 /*
- * Move all possible entries from another node before the min (i=0) or
- * after the max (i=1).  XXX can be optimized
+ * Move number of entries from another node to this node before the min
+ * (i=0) or after the max (i=1).  Expensive but not often used.
  */
 void
-Dbtux::nodeSlide(Signal* signal, NodeHandle& dstNode, NodeHandle& srcNode, unsigned i)
+Dbtux::nodeSlide(Signal* signal, NodeHandle& dstNode, NodeHandle& srcNode, unsigned cnt, unsigned i)
 {
   Frag& frag = dstNode.m_frag;
   TreeHead& tree = frag.m_tree;
   ndbrequire(i <= 1);
-  while (dstNode.getOccup() < tree.m_maxOccup && srcNode.getOccup() != 0) {
+  while (cnt != 0) {
     TreeEnt ent;
     nodePopDown(signal, srcNode, i == 0 ? srcNode.getOccup() - 1 : 0, ent);
     nodePushUp(signal, dstNode, i == 0 ? 0 : dstNode.getOccup(), ent);
+    cnt--;
   }
 }
 

ndb/src/kernel/blocks/dbtux/DbtuxSearch.cpp

@@ -159,7 +159,7 @@ Dbtux::searchToAdd(Signal* signal, Frag& frag, ConstData searchKey, TreeEnt sear
  *
  * Compares search key to each node min.  A move to right subtree can
  * overshoot target node.  The last such node is saved.  The final node
- * is a half-leaf or leaf.  If search key is less than final node min
+ * is a semi-leaf or leaf.  If search key is less than final node min
  * then the saved node is the g.l.b of the final node and we move back
  * to it.
  */

ndb/src/kernel/blocks/dbtux/DbtuxTree.cpp

@@ -18,71 +18,103 @@
 #include "Dbtux.hpp"
 
 /*
- * Add entry.
+ * Add entry.  Handle the case when there is room for one more.  This
+ * is the common case given slack in nodes.
  */
 void
 Dbtux::treeAdd(Signal* signal, Frag& frag, TreePos treePos, TreeEnt ent)
 {
   TreeHead& tree = frag.m_tree;
-  unsigned pos = treePos.m_pos;
   NodeHandle node(frag);
-  // check for empty tree
-  if (treePos.m_loc == NullTupLoc) {
+  if (treePos.m_loc != NullTupLoc) {
+    // non-empty tree
     jam();
-    insertNode(signal, node);
-    nodePushUp(signal, node, 0, ent);
-    node.setSide(2);
-    tree.m_root = node.m_loc;
-    return;
-  }
-  selectNode(signal, node, treePos.m_loc);
-  // check if it is bounding node
-  if (pos != 0 && pos != node.getOccup()) {
-    jam();
-    // check if room for one more
+    selectNode(signal, node, treePos.m_loc);
+    unsigned pos = treePos.m_pos;
     if (node.getOccup() < tree.m_maxOccup) {
+      // node has room
       jam();
       nodePushUp(signal, node, pos, ent);
       return;
     }
-    // returns min entry
-    nodePushDown(signal, node, pos - 1, ent);
-    // find position to add the removed min entry
-    TupLoc childLoc = node.getLink(0);
-    if (childLoc == NullTupLoc) {
+    treeAddFull(signal, frag, node, pos, ent);
+    return;
+  }
+  jam();
+  insertNode(signal, node);
+  nodePushUp(signal, node, 0, ent);
+  node.setSide(2);
+  tree.m_root = node.m_loc;
+}
+
+/*
+ * Add entry when node is full.  Handle the case when there is g.l.b
+ * node in left subtree with room for one more.  It will receive the min
+ * entry of this node.  The min entry could be the entry to add.
+ */
+void
+Dbtux::treeAddFull(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos, TreeEnt ent)
+{
+  TreeHead& tree = frag.m_tree;
+  TupLoc loc = lubNode.getLink(0);
+  if (loc != NullTupLoc) {
+    // find g.l.b node
+    NodeHandle glbNode(frag);
+    do {
       jam();
-      // left child will be added
-      pos = 0;
-    } else {
+      selectNode(signal, glbNode, loc);
+      loc = glbNode.getLink(1);
+    } while (loc != NullTupLoc);
+    if (glbNode.getOccup() < tree.m_maxOccup) {
+      // g.l.b node has room
       jam();
-      // find glb node
-      while (childLoc != NullTupLoc) {
+      if (pos != 0) {
         jam();
-        selectNode(signal, node, childLoc);
-        childLoc = node.getLink(1);
+        // add the new entry and return min entry
+        nodePushDown(signal, lubNode, pos - 1, ent);
       }
-      pos = node.getOccup();
+      // g.l.b node receives min entry from l.u.b node
+      nodePushUp(signal, glbNode, glbNode.getOccup(), ent);
+      return;
     }
-    // fall thru to next case
-  }
-  // adding new min or max
-  unsigned i = (pos == 0 ? 0 : 1);
-  ndbrequire(node.getLink(i) == NullTupLoc);
-  // check if the half-leaf/leaf has room for one more
-  if (node.getOccup() < tree.m_maxOccup) {
-    jam();
-    nodePushUp(signal, node, pos, ent);
+    treeAddNode(signal, frag, lubNode, pos, ent, glbNode, 1);
     return;
   }
-  // add a new node
-  NodeHandle childNode(frag);
-  insertNode(signal, childNode);
-  nodePushUp(signal, childNode, 0, ent);
+  treeAddNode(signal, frag, lubNode, pos, ent, lubNode, 0);
+}
+
+/*
+ * Add entry when there is no g.l.b node in left subtree or the g.l.b
+ * node is full.  We must add a new left or right child node which
+ * becomes the new g.l.b node.
+ */
+void
+Dbtux::treeAddNode(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos, TreeEnt ent, NodeHandle parentNode, unsigned i)
+{
+  NodeHandle glbNode(frag);
+  insertNode(signal, glbNode);
   // connect parent and child
-  node.setLink(i, childNode.m_loc);
-  childNode.setLink(2, node.m_loc);
-  childNode.setSide(i);
-  // re-balance tree at each node
+  parentNode.setLink(i, glbNode.m_loc);
+  glbNode.setLink(2, parentNode.m_loc);
+  glbNode.setSide(i);
+  if (pos != 0) {
+    jam();
+    // add the new entry and return min entry
+    nodePushDown(signal, lubNode, pos - 1, ent);
+  }
+  // g.l.b node receives min entry from l.u.b node
+  nodePushUp(signal, glbNode, 0, ent);
+  // re-balance the tree
+  treeAddRebalance(signal, frag, parentNode, i);
+}
+
+/*
+ * Re-balance tree after adding a node.  The process starts with the
+ * parent of the added node.
+ */
+void
+Dbtux::treeAddRebalance(Signal* signal, Frag& frag, NodeHandle node, unsigned i)
+{
   while (true) {
     // height of subtree i has increased by 1
     int j = (i == 0 ? -1 : +1);
@@ -131,7 +163,10 @@ Dbtux::treeAdd(Signal* signal, Frag& frag, TreePos treePos, TreeEnt ent)
 }
 
 /*
- * Remove entry.
+ * Remove entry.  Optimize for nodes with slack.  Handle the case when
+ * there is no underflow i.e. occupancy remains at least minOccup.  For
+ * interior nodes this is a requirement.  For others it means that we do
+ * not need to consider merge of semi-leaf and leaf.
  */
 void
 Dbtux::treeRemove(Signal* signal, Frag& frag, TreePos treePos)
@@ -141,100 +176,150 @@ Dbtux::treeRemove(Signal* signal, Frag& frag, TreePos treePos)
   NodeHandle node(frag);
   selectNode(signal, node, treePos.m_loc);
   TreeEnt ent;
-  // check interior node first
+  if (node.getOccup() > tree.m_minOccup) {
+    // no underflow in any node type
+    jam();
+    nodePopDown(signal, node, pos, ent);
+    return;
+  }
   if (node.getChilds() == 2) {
+    // underflow in interior node
     jam();
-    ndbrequire(node.getOccup() >= tree.m_minOccup);
-    // check if no underflow
-    if (node.getOccup() > tree.m_minOccup) {
-      jam();
-      nodePopDown(signal, node, pos, ent);
-      return;
-    }
-    // save current handle
-    NodeHandle parentNode = node;
-    // find glb node
-    TupLoc childLoc = node.getLink(0);
-    while (childLoc != NullTupLoc) {
-      jam();
-      selectNode(signal, node, childLoc);
-      childLoc = node.getLink(1);
-    }
-    // use glb max as new parent min
-    ent = node.getEnt(node.getOccup() - 1);
-    nodePopUp(signal, parentNode, pos, ent);
-    // set up to remove glb max
-    pos = node.getOccup() - 1;
-    // fall thru to next case
+    treeRemoveInner(signal, frag, node, pos);
+    return;
   }
-  // remove the element
+  // remove entry in semi/leaf
   nodePopDown(signal, node, pos, ent);
-  ndbrequire(node.getChilds() <= 1);
-  // handle half-leaf
-  unsigned i;
-  for (i = 0; i <= 1; i++) {
+  if (node.getLink(0) != NullTupLoc) {
     jam();
-    TupLoc childLoc = node.getLink(i);
-    if (childLoc != NullTupLoc) {
-      // move to child
-      selectNode(signal, node, childLoc);
-      // balance of half-leaf parent requires child to be leaf
-      break;
-    }
+    treeRemoveSemi(signal, frag, node, 0);
+    return;
   }
-  ndbrequire(node.getChilds() == 0);
-  // get parent if any
-  TupLoc parentLoc = node.getLink(2);
-  NodeHandle parentNode(frag);
-  i = node.getSide();
-  // move all that fits into parent
-  if (parentLoc != NullTupLoc) {
+  if (node.getLink(1) != NullTupLoc) {
     jam();
-    selectNode(signal, parentNode, node.getLink(2));
-    nodeSlide(signal, parentNode, node, i);
-    // fall thru to next case
+    treeRemoveSemi(signal, frag, node, 1);
+    return;
   }
-  // non-empty leaf
-  if (node.getOccup() >= 1) {
+  treeRemoveLeaf(signal, frag, node);
+}
+
+/*
+ * Remove entry when interior node underflows.  There is g.l.b node in
+ * left subtree to borrow an entry from.  The max entry of the g.l.b
+ * node becomes the min entry of this node.
+ */
+void
+Dbtux::treeRemoveInner(Signal* signal, Frag& frag, NodeHandle lubNode, unsigned pos)
+{
+  TreeHead& tree = frag.m_tree;
+  TreeEnt ent;
+  // find g.l.b node
+  NodeHandle glbNode(frag);
+  TupLoc loc = lubNode.getLink(0);
+  do {
+    jam();
+    selectNode(signal, glbNode, loc);
+    loc = glbNode.getLink(1);
+  } while (loc != NullTupLoc);
+  // borrow max entry from semi/leaf
+  nodePopDown(signal, glbNode, glbNode.getOccup() - 1, ent);
+  nodePopUp(signal, lubNode, pos, ent);
+  if (glbNode.getLink(0) != NullTupLoc) {
     jam();
+    treeRemoveSemi(signal, frag, glbNode, 0);
     return;
   }
-  // remove empty leaf
-  deleteNode(signal, node);
-  if (parentLoc == NullTupLoc) {
+  treeRemoveLeaf(signal, frag, glbNode);
+}
+
+/*
+ * Handle semi-leaf after removing an entry.  Move entries from leaf to
+ * semi-leaf to bring semi-leaf occupancy above minOccup, if possible.
+ * The leaf may become empty.
+ */
+void
+Dbtux::treeRemoveSemi(Signal* signal, Frag& frag, NodeHandle semiNode, unsigned i)
+{
+  TreeHead& tree = frag.m_tree;
+  ndbrequire(semiNode.getChilds() < 2);
+  TupLoc leafLoc = semiNode.getLink(i);
+  NodeHandle leafNode(frag);
+  selectNode(signal, leafNode, leafLoc);
+  if (semiNode.getOccup() < tree.m_minOccup) {
     jam();
-    // tree is now empty
-    tree.m_root = NullTupLoc;
-    return;
+    unsigned cnt = min(leafNode.getOccup(), tree.m_minOccup - semiNode.getOccup());
+    nodeSlide(signal, semiNode, leafNode, cnt, i);
+    if (leafNode.getOccup() == 0) {
+      // remove empty leaf
+      jam();
+      treeRemoveNode(signal, frag, leafNode);
+    }
   }
-  node = parentNode;
-  node.setLink(i, NullTupLoc);
-#ifdef dbtux_min_occup_less_max_occup
-  // check if we created a half-leaf
-  if (node.getBalance() == 0) {
+}
+
+/*
+ * Handle leaf after removing an entry.  If parent is semi-leaf, move
+ * entries to it as in the semi-leaf case.  If parent is interior node,
+ * do nothing.
+ */
+void
+Dbtux::treeRemoveLeaf(Signal* signal, Frag& frag, NodeHandle leafNode)
+{
+  TreeHead& tree = frag.m_tree;
+  TupLoc parentLoc = leafNode.getLink(2);
+  if (parentLoc != NullTupLoc) {
     jam();
-    // move entries from the other child
-    TupLoc childLoc = node.getLink(1 - i);
-    NodeHandle childNode(frag);
-    selectNode(signal, childNode, childLoc);
-    nodeSlide(signal, node, childNode, 1 - i);
-    if (childNode.getOccup() == 0) {
+    NodeHandle parentNode(frag);
+    selectNode(signal, parentNode, parentLoc);
+    unsigned i = leafNode.getSide();
+    if (parentNode.getLink(1 - i) == NullTupLoc) {
+      // parent is semi-leaf
       jam();
-      deleteNode(signal, childNode);
-      node.setLink(1 - i, NullTupLoc);
-      // we are balanced again but our parent balance changes by -1
-      parentLoc = node.getLink(2);
-      if (parentLoc == NullTupLoc) {
+      if (parentNode.getOccup() < tree.m_minOccup) {
         jam();
-        return;
+        unsigned cnt = min(leafNode.getOccup(), tree.m_minOccup - parentNode.getOccup());
+        nodeSlide(signal, parentNode, leafNode, cnt, i);
       }
-      // fix side and become parent
-      i = node.getSide();
-      selectNode(signal, node, parentLoc);
     }
   }
-#endif
-  // re-balance tree at each node
+  if (leafNode.getOccup() == 0) {
+    jam();
+    // remove empty leaf
+    treeRemoveNode(signal, frag, leafNode);
+  }
+}
+
+/*
+ * Remove empty leaf.
+ */
+void
+Dbtux::treeRemoveNode(Signal* signal, Frag& frag, NodeHandle leafNode)
+{
+  TreeHead& tree = frag.m_tree;
+  ndbrequire(leafNode.getChilds() == 0);
+  TupLoc parentLoc = leafNode.getLink(2);
+  unsigned i = leafNode.getSide();
+  deleteNode(signal, leafNode);
+  if (parentLoc != NullTupLoc) {
+    jam();
+    NodeHandle parentNode(frag);
+    selectNode(signal, parentNode, parentLoc);
+    parentNode.setLink(i, NullTupLoc);
+    // re-balance the tree
+    treeRemoveRebalance(signal, frag, parentNode, i);
+    return;
+  }
+  // tree is now empty
+  tree.m_root = NullTupLoc;
+}
+
+/*
+ * Re-balance tree after removing a node.  The process starts with the
+ * parent of the removed node.
+ */
+void
+Dbtux::treeRemoveRebalance(Signal* signal, Frag& frag, NodeHandle node, unsigned i)
+{
   while (true) {
     // height of subtree i has decreased by 1
     int j = (i == 0 ? -1 : +1);
@@ -516,6 +601,8 @@ Dbtux::treeRotateSingle(Signal* signal,
 void
 Dbtux::treeRotateDouble(Signal* signal, Frag& frag, NodeHandle& node, unsigned i)
 {
+  TreeHead& tree = frag.m_tree;
+
   // old top node
   NodeHandle node6 = node;
   const TupLoc loc6 = node6.m_loc;
@@ -549,11 +636,14 @@ Dbtux::treeRotateDouble(Signal* signal, Frag& frag, NodeHandle& node, unsigned i
   // fill up leaf before it becomes internal
   if (loc3 == NullTupLoc && loc5 == NullTupLoc) {
     jam();
-    TreeHead& tree = frag.m_tree;
-    nodeSlide(signal, node4, node2, i);
-    // implied by rule of merging half-leaves with leaves
-    ndbrequire(node4.getOccup() >= tree.m_minOccup);
-    ndbrequire(node2.getOccup() != 0);
+    if (node4.getOccup() < tree.m_minOccup) {
+      jam();
+      unsigned cnt = tree.m_minOccup - node4.getOccup();
+      ndbrequire(cnt < node2.getOccup());
+      nodeSlide(signal, node4, node2, cnt, i);
+      ndbrequire(node4.getOccup() >= tree.m_minOccup);
+      ndbrequire(node2.getOccup() != 0);
+    }
   } else {
     if (loc3 != NullTupLoc) {
       jam();

ndb/src/kernel/blocks/dbtux/Times.txt

@@ -29,6 +29,7 @@ shows ms / 1000 rows for each and index time overhead
 samples 10% of all PKs (100,000 pk reads, 100,000 scans)
 
 the "pct" values are from more accurate total times (not shown)
+comments [ ... ] are after the case
 
 040616          mc02/a  40 ms   87 ms   114 pct
                 mc02/b  51 ms  128 ms   148 pct
@@ -76,13 +77,12 @@ optim 13        mc02/a  40 ms   57 ms    42 pct
                 mc02/c   9 ms   13 ms    50 pct
                 mc02/d 170 ms  256 ms    50 pct
 
-after wl-1884 store all-NULL keys (the tests have pctnull=10 per column)
-
 optim 13        mc02/a  39 ms   59 ms    50 pct
                 mc02/b  47 ms   77 ms    61 pct
                 mc02/c   9 ms   12 ms    44 pct
                 mc02/d 246 ms  289 ms    17 pct
 
+[ after wl-1884 store all-NULL keys (the tests have pctnull=10 per column) ]
 [ case d: bug in testOIBasic killed PK read performance ]
 
 optim 14        mc02/a  41 ms   60 ms    44 pct
@@ -98,8 +98,7 @@ none            mc02/a  35 ms   60 ms    71 pct
                 mc02/c   5 ms   12 ms   106 pct
                 mc02/d 165 ms  238 ms    44 pct
 
-[ johan re-installed mc02 as fedora gcc-3.3.2 ]
-[ case c: table scan has improved... ]
+[ johan re-installed mc02 as fedora gcc-3.3.2, tux uses more C++ stuff than tup]
 
 charsets        mc02/a  35 ms   60 ms    71 pct
                 mc02/b  42 ms   84 ms    97 pct
@@ -118,6 +117,16 @@ optim 15        mc02/a  34 ms   60 ms    72 pct
 optim 16        mc02/a  34 ms   53 ms    53 pct
                 mc02/b  42 ms   75 ms    75 pct
 
-[ case a, b: binary search of bounding node when adding entry ]
+[ binary search of bounding node when adding entry ]
+
+none            mc02/a  35 ms   53 ms    51 pct
+                mc02/b  42 ms   75 ms    76 pct
+
+[ rewrote treeAdd / treeRemove ]
+
+optim 17        mc02/a  35 ms   52 ms    49 pct
+                mc02/b  43 ms   75 ms    75 pct
+
+[ allow slack (2) in interior nodes - almost no effect?? ]
 
 vim: set et:

ndb/test/ndbapi/testOIBasic.cpp

@@ -2963,9 +2963,10 @@ tbuild(Par par)
       RUNSTEP(par, createindex, ST);
       RUNSTEP(par, invalidateindex, MT);
     }
-    RUNSTEP(par, readverify, MT);
+    RUNSTEP(par, pkupdate, MT);
+    RUNSTEP(par, readverify, ST);
     RUNSTEP(par, pkdelete, MT);
-    RUNSTEP(par, readverify, MT);
+    RUNSTEP(par, readverify, ST);
     RUNSTEP(par, dropindex, ST);
   }
   return 0;